1. Field of the Invention
The present invention relates generally to processes for food, more specifically to processes for meat, and particularly to processes for meat derived from aquatic environments.
2. General Background
Two broad categories of meat are recognized: meat derived from dry land environments and meat derived from an aquatic environment. Dry land derived meat generally, as a first step in processing, have the entrails removed. E-coli, which is abundant in mammalian intestines, is a potentially lethal pathogen in food and care is required in assuring that the fecal material in the intestines of mammals is removed.
The first category is further considered in two classes: poultry and other types. Poultry is considered to be inclusive of chicken, turkey, duck and other types encompassed by USDA regulation as poultry. Other types of dry land derived meat considered to be inclusive of beef, veal pork, lamb, et cetera. USDA regulations for poultry processing specify that chicken carcasses be cooled to below forty degrees Fahrenheit within four hours of slaughter and that at least two quarts of water flow per carcass be used in chilling. Chilled water tanks are hence conventionally utilized in processing chickens in the United States and a similar procedure is applicable to other types of dry land derived meat.
Meat derived from an aquatic environment similarly considered in two broad categories, fish and shellfish. Shellfish is inclusive of mollusks and crustaceans which are filter feeders and which, by definition pass a relatively large amount of water through a structure acting as a filter for food and excrete indigestible material which is digested along with the food so obtained. The contamination of meat, generally, especially meat derived from aquatic environments, and most particularly shellfish, has become recognized as a problem of tremendous importance in relatively recent years. Shellfish are filter feeders and therefore perhaps logically quite sensitive to and readily affected adversely by contamination of the pertinent aquatic environment.
The loss of substantial shellfish harvest in the Gulf of Mexico to the contamination of those waters by the effluent carried largely by the Mississippi River is an example of the loss of shellfish and more generally of meat derived from aquatic environments due to contamination. The ingestion of contaminated shellfish is further known as the cause of hundreds on incident of illness annually in the United States. The main concern is recognized as bacteriological contamination by foodborne pathogens including pseudomonas, vibrio, salmonella, and listeria which are also known as the spoilage microflora.
The particular problem concerned, moreover, is considered to have several components. The first component, contamination of aquatic environment is regarded as a given condition which varies considerably by geography. The second component is minimization of the shellfish contamination consequent the initial contamination. Irradiation is one known means of reducing spoilage microfloral populations but irradiation is also known to be destructive of food stuffs generally and shellfish particularly. The third component is determination of the level of contamination present in the shellfish at a given time, especially before and after processing as suggested in this invention. Accurate and timely determination of contamination levels would facilitate minimization of irradiation utilized and the adverse effects to the shellfish caused by the same.
3. Discussion of the Prior Art
The large scale irradiation of meat derived from aquatic environments is not presently permitted in the United States. The determination of pathogen level from a sample of meat is conventionally conducted with use of cultures grown in an appropriate medium, typically a gel, such as agar which undergoes a period of incubation in order to develop colonies which may be accurately measured. The length of time required for accurate determination of a pathogen level varies according, mainly, to the growth rate of the pathogen. This is typically on the order of 48-72 hours unless optical devices are employed which measure the opacity of a fluid sample as opposed to the colony growth in a petri dish. An accurate indication of pathogen level may be achieved, depending upon the pathogen, in six to twelve hours with use of optical opacity measuring devices.
U.S. Pat. Nos. 3,594,115, 3,699,437, 3,781,659 and 4,140,649 are referenced along with Canada No. 561,924 and Japan No. 62-100241. The first two U.S. patents and the last two foreign patents were cited by the examiner in U.S. Pat. No. 5,482,726 issued to the present applicant. The other two patents referenced were both issued to Amiram Ur MD and relate to the detection of blood coagulation by the use of conductivity cells measuring electrical impedance through fluid samples therein. The technology described in these two patent issued to Dr. Ur is concerned with the testing of human blood samples, specifically the rate of blood coagulation, which rate is valued as an indicator in many medical queries.
In addition to the above cited patents, it is noted that the use of ultrasound has been mentioned in the known prior art as a means of providing agitation to a bath of sanitizing solution for treating carcasses. xe2x80x9cThe sanitizing solution is preferably aerated or agitated during use in the tank. The sanitizing solution may be agitated through the use of ultrasound, paddles, brushes or other physical means. Aeration may be by bubbling or by other physical means. Aeration may be by bubbling or by other methods well known in the Artxe2x80x9d (U.S. Pat. No. 5,234,703, Col. 5, lines 58-62). It is noted that this disclosure is of a particular sanitizing solution used in a conventional manner in accordance with detailed USDA procedures, claim 1 of said patent reading:
xe2x80x9cA method for treating an animal carcass to eradicate bacteria from the carcass comprising:
(a) contacting the carcass with an aqueous solution having an effective amount of a medium chain fatty acid and a sufficient amount of an acid to maintain said solution at an acid pH.xe2x80x9d
In summary of the prior art it is first noted that irradiation with cobalt60 is known as a common practice in the control of bacteriological contamination of certain edible food including spices and grain and that irradiation is approved by the USDA for beef, poultry and pork. It is secondly noted that conventional practice in the determination of pathogen level in meat involves the use of incubated cultures optically measured and that a determination of the rate of blood coagulation using conductivity cells through which changes in electrical impedance of samples held therein is known in the medical field. Thirdly, it is noted that ultrasound has been mentioned in the pertinent prior art as a means of providing agitation to a bath of sanitizing solution for carcasses which is considered in the prior art to be functionally equivalent to the use of paddles or brushes. Fourthly, it is noted that DNA sequence analysis methods can be used to identify specific strains of contaminants.
Statement of Need
Because contamination of meat is a serious problem, resulting in the loss of significant amounts of otherwise available harvest of the same and the illness of many people annually in the United States and because irradiation is known to be useful in destroying bacteriological contamination, there is considered a need for a method of ensuring an uncontaminated condition of meat, particularly meat derived from aquatic environments which is not excessively destructive of the meat, further preferably including means for the amelioration of the effects of the contamination of said meat.
Objects of the Invention
The preeminent objective of the invention is the provision of a method by which the quality regarding both pathogen contamination level and integrity of meat products is ensured during processing.
An auxiliary object of the present invention is the reduction of pathogen contamination of shellfish (meat) by use of irradiation.
An ancillary object of the present invention is the minimization of the irradiation required for reduction of pathogen contamination of meat by utilizing rapid determination of pathogen contamination level in meat in association with irradiation.
A second ancillary object of the present invention is the minimization of the irradiation required for reduction of pathogen contamination by utilizing ultrasonic baths for microscopic exterior cleansing of meat in association with irradiation.
A third ancillary object of the present invention is to determine genetic variations of foodborne neoplasms and pathogens such as hepatitis A and the immunodeficiency viruses (HIV) by utilization of mutant genomic assays.
Principles Relating to the Present Invention
In obtainment of the above stated objects the following elements are considered to be fundamental: (a) rapid detection of pathogen levels and rapid confirmation of neoplasm presence (b) pathogen reduction in meat by means of irradiation; (c) minimization of the destruction of the integrity of meat associated with irradiation by means of rapid determination of a pathogen contamination level; (d) minimization of the destruction of the integrity of meat associated with irradiation by means of microscopic cleansing of meat exterior surfaces effected with utilization of an ultrasonic bath; (e) minimization of the destruction of the integrity of meat associated with irradiation by means of enhanced depuration of shellfish effected with utilization of an ultrasonic bath; and (f) determination of genomic variations for (pathogenic) strain identification. Many other particular considerations are associated with a practical method utilizing a combination of the above stated fundamental elements according to the type of meat addressed.
As mentioned earlier, processing of mammalian meat includes removal of fecal material as a first step. The intestines and fecal material of fish may also be removed as a first step in processing. This is not true for shellfish. Shrimp may be decapitated in order to remove the majority of pathogens thereby. Mollusks are simply thrown on ice. Because shellfish are filter feeders. However, a large amount of contamination typically found therein maybe purged by natural processes. Ultrasonic waves applied to a tank holding live shellfish accelerates the natural deputation process. Ultrasonic waves of sufficient energy intensity applied to a tank containing solid objects immersed in the fluid held therein will cause cavitation to impinge upon the exterior surfaces of the immersed objects. This use of ultrasound in a tank containing an aqueous medium may be applied to any type of meat in order to cleanse the exterior surface of the meat microscopically.
Removal of the fecal material and the use of ultrasound for both microscopic exterior cleansing of meat and enhanced depuration of live shellfish provide both comprised means of minimizing the contamination of meat during processing of the same. Further reduction of pathogen level by irradiation is recommended, particularly in association with methods of rapid detection of pathogen levels in order to minimize the irradiation utilized and the destruction of the integrity of the meat irradiated. Use of an electron beam generator is recommended as a cold source of irradiation which is opposed to a hot source such as cobalt60.
The basic method for rapid detection of pathogen level is also applicable to detecting the presence of malignant tumors, i.e., neoplasms in animal tissue. The electrical impedance of a fluid sample of meat tissue is measured over time. The meat is no longer alive and normal cell division has ceased. Cell division by both pathogens and neoplasms, however, continues and is detectable using balanced circuitry having two arms each electrically connected to one of two electrodes disposed upon either end of a conductive cell. Two such cells are utilized wherein one cell acts as a reference and the other test cell. The reference may have a thin film of a specific inhibitor of the activity monitored in the sample placed in the cell. Alternatively, the reference sample may have a specific inhibitor placed in solution with the sample which is otherwise identical with the test sample.
When a known deoxyoligomer probe hybridizes a complementary DNA target and generates a mismatch, the specific cleavage at the mismatch by mismatch repari enzymes reveals the base of a mutation in the DNA target or a specific DNA sequence such as an infectious microorganism (Hsu et al 1998). For biological samples of genetic or infectious diseases, a direct detection of mismatch cleavage needs a sensitivity able to detect a few million or even a few target DNA molecules (Hsu et al 1992). Amplification of the mismatch cleavage at the probe has improved the detection of human immunodeficiency virus (HIV) target and mutated bacterial and human DNA sequences (Craig et al 1996).
The assay relies on the high mismatch specificity of mutant proteins. The estimated sensitivity of the assay currently is up to 1%. Thus, a single base change in genomic DNA from tumor cells that are present in only 1% of normal cell background can be detected by this method. Research suggest, mismatch repair enzymes have an amino binding site that forms the Schiff base of the deoxyribose in the target DNA substrate (Hsu et al 1998).